Actual versus ideal performance of a SOFC mCHP unit ... · PDF fileActual versus ideal...

Actual versus ideal performance of a SOFC mCHP unit

operating in a domestic building

Hydrogen & Fuel Cell SUPERGEN Researcher Conference

15 – 17th December 2014

Birmingham, UK

Theo Elmer1, 2, Mark Worall1, Shenyi Wu1 and Saffa B Riffat1

1Architecture, Climate and Environment Research Group, The University of Nottingham 2CDT Hydrogen, Fuel Cells and their Applications, University of Birmingham

*corresponding author email: [email protected]

mailto:[email protected]

Presentation outline

Wednesday, 21 January 2015 H2FC SUPERGEN Researcher Conference 2

1. Introduction

2. Aims and objectives

3. mCHP and fuel cell technology

4. The scenarios studies

5. Assessment method

6. Actual assessment data

7. Emission assessment results

8. Economic assessment results

9. Combined efficiency results

10. Conclusions

11. Acknowledgements and references

1. Introduction Future energy supply must be secure, clean and economic

EU committed to reduce CO2 emissions by 20% by 2020 compared to 1990 levels [1]

European buildings account for 40% of energy demand [2] and 50% of CO2 emissions [3]

Built environment identified as holding the largest economic potential for the reduction of

CO2 emissions – IPCC [4]

Wednesday, 21 January 2015 3

CLEAN ECONOMIC

SECURE

FUTURE

ENERGY

SUPPLY

Fuel cell mCHP is a possible option for decentralised low carbon energy generation

H2FC SUPERGEN Researcher Conference


2. Aims and objectives

The aim of this work is to assess the emission and economic performance of a SOFC

mCHP system (BlueGEN) operating in a domestic home.

The assessment will compare three scenarios:

1. Base case – boiler and grid electricity

2. Ideal case – BlueGEN operating at quoted manufacture performance

3. Actual case – BlueGEN real operational data i.e. fluctuating electrical power output and

efficiency

In each scenario, the following assessments will be made:

i. Emission assessment – the difference in kg CO2 per scenario investigated

ii. Economic assessment – the cost difference (£) per scenario investigated


3. mCHP and FC technology

Wednesday, 21 January 2015 5 H2FC SUPERGEN Researcher Conference

mCHP advantages [5]

1. Improved system efficiency 2. Reduction in NRPE demand

3. Transmission loss reduction 4. Environmental / economic benefit

5. Utility scale decarbonisation

FC advantages [5]

1. High electrical efficiency 2. Low H:P

3. Low / no harmful emissions 4. Near silent operation

5. Flexibility of fuel use


(1) Base case scenario (2) SOFC mCHP ideal case

(3) SOFC mCHP actual case

4. The scenarios studied

Grid

electricity

Natural

gas

Natural

gas

Grid

electricity

SOFC

Boiler

Boiler


The SOFC used in this study is the commercially available

BlueGEN 1.5kWe SOFC mCHP unit

Assessment location - David Wilson House, CEH ,UoN

No WHR

With WHR

With TES

5. Assessment method


0 50 100 150 200 250 300 3500

10

20

30

40

50

60

70

Day number

Ener

gy

dem

and

(k

Wh

)

Electrical demand (kWh)Electrical demand (kWh)

Space heating demand (kWh)Space heating demand (kWh)

DHW demand (kWh)DHW demand (kWh)

David Wilson House energy load profile BlueGEN SOFC mCHP system

Auxiliary gas

boiler

Heat recovery

circuit

SOFC unit

Annual thermal demand 7814 kWh

Annual electrical power demand 4525 kWh

Annual H:P demand ratio ~ 1.75

Operates on natural gas

Runs continuously at 1.5kWe Import / export of electricity Supplemented with auxiliary gas boiler

Qualifies for UK export and feed in tariffs


Hourly power and thermal demand data is known for the house

Hourly electrical power and thermal output data for BlueGEN is known

Energy balances completed at each hour for the three scenarios studied

SOFC performance summary Ideal Actual

Electrical power 1.5 kW Variable

Electrical efficiency 60 % Variable

CHP efficiency 85 % Variable


1. Burner ignited

2. Power export begins 3. Issue with water leak and PRV 4. Gas supply turned off

5. Stack failure

0 500 1000 1500 2000 2500 3000 3500 4000

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

Time [Hours]

Ou

tpu

t p

ow

er

[kW

]

BlueGEN electrical output - whole periodBlueGEN electrical output - whole period

90.5 % availability for power generation (3967 hours)

88.4 % availability for power generation at ηe ≥ 50% (3877 hours)

BlueGEN SOFC operational from 25th March 2014

Ran for six months, until stack failure on 12th September 2014

Six months’ worth of operational data for the unit in this period (4386 hours)

The assessment presented is for this six month period

March 2014 September 2014

6. Actual assessment data

0 500 1000 1500 2000 2500 3000 3500 4000-10

0

10

20

30

40

50

60

70

80

Time [Hours]

Ele

ctr

ica

l e

ffic

ien

cy [%

]

BlueGEN electrical efficiency - whole periodBlueGEN electrical efficiency - whole period

1

34

5

2


7. Emission assessment results Emissions analysis constants Value (kg CO2 / kWh)

Grid electricity 0.555

CCGT electricity (offset export) 0.36

Natural gas emission factor 0.184

For the TES scenario:

(a) An average 55 % reduction over the

6 month period (base & actual)

(b) An average 24 % difference over the

6 month period (ideal and actual)

(c) An average 66 % reduction over the

6 month period (base & ideal)

0 500 1000 1500 2000 2500 3000 3500 4000-0.25

-0.125

0

0.125

0.25

0.375

0.5

Time [Hours]

CO

2 e

mis

sio

ns [kg

]

Base case CO2

Real CO2 -TESReal CO2 -TES

Ideal CO2 - TESIdeal CO2 - TES

(a)

(b) (c)

Actual case

Added value of the FC (no WHR & TES)

35 % reduction with base case

Added value of WHR (no TES)

29 % reduction with FC no WHR & TES

Added value of TES

2 % reduction with FC with WHR no TES

No grid connection with WHR & TES

41 % increase with base case

Actual case Ideal case % difference

Base case (kg CO2) 1456.79 --- ---

FC with no WHR (kg CO2) 941.02 784.54 16

FC with WHR no TES (kg CO2) 667.65 533.36 20

FC with WHR & TES (kg CO2) 653.31 497.61 24


0 500 1000 1500 2000 2500 3000 3500 4000-0.25

-0.125

0

0.125

0.25

Time [Hours]

Co

st [£

]

Base case cost

Real cost -TESReal cost -TES

Ideal cost - TESIdeal cost - TES

Economic analysis constants Value (£/kWh)

Grid electricity 0.172

Natural gas 0.0421

mCHP FiT (OFGEM) 0.125

Export tariff (OFGEM) 0.045

8. Economic assessment results

Base

case

Ideal

case

Actual

case

% difference

(base & ideal)

% difference

(base & actual)

Cost (£) – EXT & FIT 427.14 - 476.99 - 441.37 212 % reduction 203 % reduction

Cost (£) – just EXT --- 262.38 298.01 39% reduction 30 % reduction

Cost (£) – no tariffs --- 437.70 473.33 2 % increase 11 % increase

(a)

(b)

(c)

For the TES scenario (all tariffs):

(a) An average 203 % reduction over

the 6 month period (base & actual)

(b) An average 8 % difference over the

6 month period (ideal and actual)

(c) An average 212 % reduction over

the 6 month period (base & ideal)

Actual case – ALL tariffs

Added value of the FC (no WHR & TES)

188 % reduction with base case

Added value of WHR (no TES)

17 % reduction with FC no WHR & TES

Added value of TES

1 % reduction with FC with WHR no TES


9. Combined efficiency results

Grid connection provides greater added value to CHP efficiency than TES

does, shown in the difference between the red and green lines

0 500 1000 1500 2000 2500 3000 3500 40000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Time [Hours]

CH

P e

ffic

ien

cy

Grid & TES

Grid & no TESGrid & no TES

No grid & TESNo grid & TES

No grid no TESNo grid no TES

Ideal 85% CHP efficiency with TES and grid

15% drop from ideal 85% CHP efficiency



~ 27 % difference

10. Conclusions


The aim of this work has been to assess the emission and economic performance of a

SOFC mCHP (BlueGEN) system operating in a domestic home, under three scenarios:

1. Base case – boiler and grid electricity

2. Ideal case – operating at quoted manufacture performance

3. Actual case – real operational data


Specific conclusions from the work presented: 1. The BlueGEN system can provide considerable emission reductions and economic benefit compared

to the base case scenario – for both the actual and ideal cases

2. Grid interaction is essential for significant emission and cost reductions compared to the base case 3. Government incubator support significantly improves the economic performance (EXT / FIT) 4. For the six month assessment period there is reasonable difference between the real and ideal

performance of the system ~ 24 % for emission and 8 % for economic analysis. Differences attributed to issues of accelerated electrical efficiency degradation (components, gas shut off etc.)

5. WHR and TES do provide added benefit to the system performance, however it is not as significant as grid interaction

General conclusions from the work presented: 1. The increased reliance on natural gas in the case of the BlueGEN SOFC mCHP system needs

consideration, as this could have serious implications for the development of a more robust and secure energy system, less reliant on foreign imports of energy

2. The use of natural gas fed fuel cell technology today will provide an essential stepping stone to a future

low carbon economy based upon hydrogen


0 500 1000 1500 2000 2500 3000 3500 4000 4500-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Time [Hours]

Ou

tpu

t p

ow

er

[kW

]

1

3

4 52

6

7

1. Burner ignited

2. Power export begins 3. Issue with water leak and PRV 4. Gas supply turned off

5. Stack failure 6. Stack replacement – 13.11.2014

7. Power export – 22.11.2014

Post stack replacement

11. Acknowledgements and references


ACKNOWLEDGEMENTS

The authors would like to acknowledge the support from European Commission under the Fuel Cell and Hydrogen Joint Undertaking Initiative (FCH-JU) for the “Durable low temperature solid oxide fuel cell Tri-generation system for low carbon buildings” project, agreement No. 303454. The authors would also like

to thank the EPSRC and CDT in Hydrogen, Fuel cells and their Applications for their continued financial and academic support.

REFERENCES [1] Böhringer, C., T.F. Rutherford, and R.S.J. Tol, THE EU 20/20/2020 targets: An overview of the EMF22

assessment. Energy Economics, 2009. 31, Supplement 2(0): p. S268-S273. [2] Ekins, P. and E. Lees, The impact of EU policies on energy use in and the evolution of the UK built

environment. Energy Policy, 2008. 36(12): p. 4580-4583. [3] Clarke, J.A., Johnstone, Cameron M., Kelly, Nicolas J., Strachan, Paul A., Tuohy, Paul, The role of built environment energy efficiency in a sustainable UK energy economy. Energy Policy, 2008. 36(12): p. 4605-

4609. [4] Hawkes, A., et al., Fuel cells for micro-combined heat and power generation. Energy & Environmental

Science, 2009. 2(7). [5] Elmer, T., Worall, M., Wu, S., Riffat, S., "Fuel cell technology for domestic built environment applications: State of-the-art review," Renewable and Sustainable Energy Reviews, vol. 42, pp. 913-931,

2015. [6] Conroy, G., A. Duffy, and L.M. Ayompe, Economic, energy and GHG emissions performance

evaluation of a WhisperGen Mk IV Stirling engine μ-CHP unit in a domestic dwelling. Energy Conversion and Management, 2014. 81(0): p. 465-474.


Thank you

Questions welcome

www.trisofc.com

Hydrogen & Fuel Cell SUPERGEN Researcher Conference

15 – 17th December 2014

Birmingham, UK

http://www.trisofc.com/

Actual versus ideal performance of a SOFC mCHP unit ... · PDF fileActual versus ideal...

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